test: make test-http(s)-set-timeout-server alike

Make test-http(s)-set-timeout-server tests more similar and resolve the
following issues:

* `test-http-set-timeout-server.js` had a `secReceived` check in
  `serverResponseTimeoutWithPipeline()` that was added to prevent
  flakiness, but this did not exist in the https counterpart.

* `test-https-set-timeout-server.js` utilized `common.mustCall()`,
  `common.mustNotCall()`, etc., while the http counterpart utilized the
  old method of checking flags on exit of the process.

Refs: https://github.com/nodejs/node/issues/13588
PR-URL: https://github.com/nodejs/node/pull/13625
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Alexey Orlenko <eaglexrlnk@gmail.com>

test/sequential/test-https-set-timeout-server.js

@@ -137,19 +137,24 @@ test(function serverRequestNotTimeoutAfterEnd(cb) {
 
 test(function serverResponseTimeoutWithPipeline(cb) {
   let caughtTimeout = '';
+  let secReceived = false;
   process.on('exit', function() {
     assert.strictEqual(caughtTimeout, '/2');
   });
   const server = https.createServer(serverOptions, function(req, res) {
+    if (req.url === '/2')
+      secReceived = true;
     res.setTimeout(50, function() {
       caughtTimeout += req.url;
     });
     if (req.url === '/1') res.end();
   });
   server.on('timeout', function(socket) {
-    socket.destroy();
-    server.close();
-    cb();
+    if (secReceived) {
+      socket.destroy();
+      server.close();
+      cb();
+    }
   });
   server.listen(0, function() {
     const options = {